How to charge your electric car with solar panels

Solar panels generate free, clean electricity – so naturally, you’ll want to use it to power everything in your life.

Charging your electric vehicle with solar electricity can save you hundreds of pounds, slash your carbon footprint, and reduce your dependence on public charging stations and the grid.

Perhaps that's why it's rapidly gaining in popularity. 29% of EV drivers have solar panels, according to a 2023 survey by Zapmap, which is six times higher than the national average.

In this guide, we’ll explain how using solar panels to charge an electric car works, what the best setup is, how much it costs upfront, and how much you can save.

If you would like to see the savings you could get from a solar & battery system, answer a few questions below and we’ll provide an estimate.

How does it work?

If you buy an EV charger that isn’t fully compatible with solar panels, it will still use the electricity your panels generate, either while it’s being produced or from your solar battery, if you have one.

However, you won’t be able to control what source your charger uses; it’ll simply draw electricity from wherever it can.

That means it’ll probably use some grid electricity if you charge your car during the day, to meet the peak power rating of your EV charger.

To ensure that you’re charging your EV with solar, you’ll need a technologically advanced ‘solar charger,’ which allows you to power your car with solar electricity more effectively, with more options.

These chargers usually come with a CT (Current Transformer) clamp that automatically turns the charger on when it senses your solar panels are generating electricity.

The rest of the time, your charger either won’t fill your car’s battery at all, or will do so using grid electricity – but relatively slowly.

When compared to a regular EV charger, a solar charger can significantly increase how much of your solar electricity you use to charge your car.

This will allow you to cut your electricity bills, and ensure your EV is always sufficiently charged.

A little more detail

An EV charger will usually provide your car with electricity at a consistent rate, which for domestic charging points is usually around 7kW. This is like measuring your shower's water pressure, in that it tracks how quickly the electricity comes out.

A solar-compatible charger allows you to adjust this rate to align it with the amount of electricity your solar panels are generating – and it's even easier to run your car on solar if you get a smart EV charger.

These devices can automatically sync up your charging rate with your solar generation rate, and give you the option to power your car with excess solar electricity, rather than exporting it to the grid.

They do this via a CT clamp, which tracks electricity as it moves between your home and the grid. It'll notify your smart charger whenever your solar panels are producing more electricity than your home's using, and your charger will lower its rate to match.

This allows you to always charge your EV with solar-generated electricity, no matter how much daylight there is or how intense it is.

Do you need a battery as well?

A storage battery is a good idea, though not necessarily in terms of charging your EV.

Having a battery can further cut your energy bills, as it allows you to consume more of the electricity your solar panels generate each day.

Though your solar panels' output can provide some of the electricity your EV needs, it'll almost certainly be most profitable for you to get the rest of your car's electricity by signing up to a time of use import tariff for EV drivers.

That way, you can charge your EV at night on a cheap off-peak rate, and use the electricity in your battery to power your home throughout the day, reducing the amount you have to import from the grid.

This is usually the best way to use your battery, though if you're on one of the best export tariffs, you may earn more money by selling this electricity to the grid.

It also may not be the best idea to charge an EV with a storage battery because any solar-generated electricity used will generally have to be converted from direct current (DC) electricity to alternating current (AC), then back to DC again.

This process causes an unnecessary amount of transmission loss when compared to grid electricity, which only requires one conversion from AC to DC.

How to stop your battery charging your EV overnight

Some storage batteries allow you to set their charging and discharging times and behaviours, including whether or not they prioritise powering your EV.

If you own one of these models, you should be able to tell your battery not charge your EV at night, so you can take advantage of cheap overnight rates instead.

What are the best EV chargers for solar charging?

These are the best electric car chargers for solar charging, because they’re designed to be compatible with solar panel systems.

Most chargers aren’t designed in this way. They can still use the electricity your solar panels produce, but you won’t be able to choose how much solar electricity they use.

Fortunately, at this stage in their technological development, it’s relatively easy to find solar-compatible EV chargers.

Here’s a rundown of all the models that are optimised to use solar-generated electricity.

1. Save money on charging

You’ll save around £400 per year on charging costs by getting electricity from your solar panels instead of the grid, on average.

This saving rises to £770 when you compare it to using public charging stations, which typically charge a significant premium.

And just in case you were still wondering whether you should switch to an EV, it’s around £1,000 cheaper to run a car on your own solar electricity rather than petrol.

2. Maximise your savings with smart tariffs

If you use a smart tariff like Intelligent Octopus Go, you can save as much as possible, reaching and even exceeding the figures mentioned above.

You can use the app to set how much charge you need and when you need it, and Octopus will automatically charge your car when it’s cheapest.

This may mean using the solar electricity your panels generate, or if it’s nighttime and you don’t have a battery, the charger may use grid electricity – but for just 7p per kWh (kilowatt-hour).

Some other energy suppliers offer EV tariffs with a cheap off-peak rate that means you can save by charging your car at a specific time of the day – which is much less flexible.

3. Cut your carbon footprint

With the sun powering the great majority of your driving, you’ll typically save 248kg of CO2 per year, in addition to the 1.5 tonnes you save by driving an EV instead of a petrol car.

Electricity from the national grid is much greener than it used to be, but still emits 149g of CO2 per kWh.

The average EV owner requires 2,029kWh to power their annual driving distance of 6,600 miles, around 82% of which can typically be supplied with solar panels, according to our calculations.

Due to seasonal variations in daylight hours, the remaining 18% will typically be supplied by the grid.

Your solar panels will still likely produce excess electricity during the summer and spring, which you can use at home or sell to the grid, reducing your carbon footprint even further.

4. Protect yourself against energy price rises

Solar panels enable you to cut your reliance on the electricity grid.

This softens the blow of any price cap rises, as your EV charging needs can mostly be fulfilled by your solar panels.

For example, if the price of electricity rose by 10%, this would naturally add 10% to your EV charging costs – but if you only rely on the grid for 18% of your car’s electricity every year, you’ll barely notice the difference.

As of November 2024, it’d work out to an increase of £9 per year, on average.

How many solar panels do you need to charge an electric car?

On average, you need six solar panels to charge an electric car – assuming each panel has a peak rating of 400W.

However, the average three-bedroom household that’s looking to power its appliances and charge an EV will need a 5.9kWp system, which is 14 solar panels at 400W each.

How much does it cost to charge an electric car with solar panels?

When is the best time to charge an electric car with solar panels?

The best time to charge an electric car with electricity from your solar panels is around the middle of the day, when the sun is highest in the sky and your system is generating the most energy.

This is often the point when your panels are generating more electricity than you can use, so instead of sending it to the grid through one of the best export tariffs, you can use it to charge your car.

However, if you have a solar battery, you can store this electricity to use in the evening or night, meaning your car doesn’t have to be home during the day to be charged.

If you’re on a smart charging tariff like Intelligent Octopus Go and you need to top-up your car’s battery further, you can then charge your car from the national grid for just 7p per kWh, any time between 11:30pm and 5:30am.

How long does it take?

It'll take around six hours to charge the average electric vehicle from 20% to 80%, using a standard 7kW charger.

If you charge your EV during the day, some of this electricity will come from your solar panels, and some will come from the grid.

With a solar charger, you can set it to automatically charge your car’s battery when your solar panels are generating excess electricity.

Unless you have a solar panel system that generates a tremendous amount of electricity, you won't be able to run your EV on 100% solar power, but you can still massively cut your bills.

It’s usually best to charge your car to no more than 80%, both to lengthen your battery’s lifespan and because it takes roughly the same amount of time to charge up to 80% as it does to charge from 80% to 100%.

You can absolutely charge your car to 100%, but it’ll degrade the battery slightly every time you do, so it’s best to only do so before a long trip. When you do so, it’ll take around 10 hours.

There’s also no harm in discharging your electric vehicle below 20% – as long as you don’t leave it that way for weeks or months – but it’s always safer to have some electricity left in your battery, just in case.

Charging in the summer vs winter

Since we have seasons in the UK, the amount of daylight hours varies across the year – which means your solar panels will generate more in some months than others.

That means you’ll need to use more grid electricity to charge your car during the winter months, when the days are shorter and the skies are cloudier.

On the flip side, your panels will usually generate more electricity than you can use in summer, which means you can massively cut your EV charging bills and sell the excess to the grid with a solar export tariff.

You can see this generation pattern in the output chart below, which is based on a four-bedroom home in Essex with a 6kWp solar panel system and 5kWh battery. The system produces almost 25kWh of electricity per day in May and July, but just 4.9kWh each day in December.

How popular is EV solar charging?

We can safely assume that EV solar charging is increasingly popular in the UK.

EV drivers are seven times more likely to have solar panels at home than the average UK household, according to Zapmap's 2023 survey.

There's no data telling us exactly how many people have both solar panels and an EV, but we do know through Zapmap that 29% of EV drivers have gone solar.

The UK has 1,299,055 EVs as of October 2024, so if we assume they all belong to different households, we can say 376,726 homes have an EV and solar panels.

There are twice as many EVs on the road as there were in 2022, and roughly 27% more solar homes, according to government data – all of which paints an extremely promising picture when it comes to solar EV charging.

Number of EVs and households with solar panels in the UK, 2020-24

Next steps

You now have all the information you need to decide whether or not you want to use solar panels to cut hundreds of pounds off your annual EV charging costs.

All that’s left is to choose a solar panel system – and ideally, a solar-compatible EV charger to go with it.

If you’re wondering how much a solar & battery system could save you, just answer a few questions below, and we’ll provide you with an estimate.

Charging an EV with solar: FAQs